1. Field of the Invention
The invention relates to a control device and a control method for an internal combustion engine for controlling an internal combustion engine capable of using a blended fuel in which, for example, several kinds of fuels are blended.
2. Description of the Related Art
Generally, internal combustion engines that use various types of fuels, including internal combustion engines capable of using the aforementioned kind of blended fuel, require a suitable contrivance in order to secure driveability. For example, if the amount of fuel injection is reduced when an idle operation is being performed following the completion of cranking and the engine rotation speed is a low speed, for example, an idling rotation speed, a drop in the engine rotation speed to below the idling rotation speed occurs, and degrades the driveability (e.g., causing a lean misfire, knocking, faults due to an exhaust gas temperature rise, etc.). To cope with such faults, a technology regarding internal combustion engines that mainly use a common fuel, for example diesel or the like, has been proposed in which the maximum fuel injection amount is restricted at the time of cranking, and after the end of cranking, the injection amount is increased to or above a control amount (see Japanese Patent Application Publication No. 2006-2706 (JP-A-2006-2706)). According to this technology, a drop of the engine rotation speed following the end of cranking at the time of start of the engine is restrained. Then, the loss in driveability can be restrained.
However, the foregoing technology disclosed in Japanese Patent Application Publication No. 2006-2706 (JP-A-2006-2706) can suffer from the following problems. That is, in the technology disclosed in Japanese Patent Application Publication No. 2006-2706 (JP-A-2006-2706), consideration is given regarding the time of starting the engine, but no consideration is given regarding the time of full load occurring after the elapse of a certain amount of time following the starting of the engine. Therefore, there is a possibility of an undesired event as follows. That is, at the time of full load, a proper injection amount cannot be secured or the injection end timing may become retarded, and therefore the output produced may become lower than an assumed value or may become unstable, thus resulting in a deteriorated driveability or a deteriorated combustion. Therefore, in order to truly secure a driveability, it is necessary to suitably adjust the injection amount not only at the time of starting the engine, but also at other times. Furthermore, in a situation where besides gasoline, a blended fuel in which several kinds of fuel, such as alcohol or the like, are blended is used, which trend is recently increasing from the viewpoint of alternative energy, the securement of driveability as mentioned above is becoming increasingly difficult.